Pathways to Naturally Small Dirac Neutrino Masses

TL;DR

This paper explores mechanisms for naturally small Dirac neutrino masses through symmetries, analyzing tree-level and one-loop processes, and introduces a scotogenic left-right model for this purpose.

Contribution

It systematically studies how symmetries can produce small Dirac neutrino masses at tree level and one loop, and proposes a new scotogenic left-right model.

Findings

Small Dirac neutrino masses can be naturally achieved with specific symmetries.

A novel scotogenic left-right model is proposed for one-loop mass generation.

The model provides a framework for understanding neutrino mass smallness.

Abstract

If neutrinos are truly Dirac fermions, the smallness of their masses may still be natural if certain symmetries exist beyond those of the standard model of quarks and leptons. We perform a systematic study of how this may occur at tree level and in one loop. We also propose a scotogenic version of the left-right gauge model with naturally small Dirac neutrino masses in one loop.